Photoluminescence and photoelectric properties of CdTe crystals doped with Er atoms

The low-temperature photoluminescence (PL) and photodiffusion spectra of CdTe crystals doped with Er atoms were measured. The most intensive and narrow line in the PL spectrum is A°X-line which is caused by the emission of an exciton bound to a neutral center associated with Na residual impurity. The presence of Na atoms in CdTe:Er crystals is supported by observation of recombination between electrons of the conduction band and acceptor levels associated with these impurity atoms. Other PL bands caused by optical transition with participation of donor-acceptor pairs (DAP) are also observed. It is shown that in this case P acceptor centers and donors caused by the presence of Al atoms situated in the Cd sites take part in the recombination process. The PL bands associated with recombination of DAP which include the complex acceptor centers do not appear in the PL spectra. Our findings indicate a high optical quality of the crystals. Thus, they provide a way to improve structural properties of CdTe crystals using the ability of rare earth (RE) elements to react with residual impurities in semiconductor materials. This is a result of the manifestation of so-called “cleaning” process of the semiconductor materials by their doping with RE elements.